What do you need in a calendar service that you can't find elsewhere?
I use the Calendar app with NextCloud[0] for a CalDAV server + calendar web interface. It's fully-featured as far as I can tell. I use its CalDAV functionality to sync to my Android phone using DAVx^5[1], which integrates the calendars natively so that you can use whatever calendar app you want on your phone (I use Etar[2]).
Ah, gotcha. There are hosted Nextcloud solutions out there if you can't run your own instance. I've never used them and can't speak to how non-technical the overall process is (I'd guess it varies by provider).
Nextcloud's website does have a page on getting ("free"?) accounts from providers. It took me a hot second to find the "change provider" link, but that allows you to see a bunch of options.